API Reference

Next.js API Quick Reference

Curated reference of the most-used Next.js framework APIs. For the complete API reference, see the official docs.

Navigation & Routing Functions

redirect(path, type?)

Server-side redirect. Throws internally — do not wrap in try/catch.

import { redirect } from 'next/navigation'

export default async function Page() {
  const session = await getSession()
  if (!session) redirect('/login')
  // ...
}

notFound()

Trigger the nearest not-found.tsx boundary.

import { notFound } from 'next/navigation'

export default async function Page({ params }: { params: Promise<{ id: string }> }) {
  const { id } = await params
  const post = await getPost(id)
  if (!post) notFound()
  return <div>{post.title}</div>
}

useRouter() (Client Component only)

Programmatic navigation in Client Components.

'use client'
import { useRouter } from 'next/navigation'

export default function Form() {
  const router = useRouter()
  // router.push('/dashboard')
  // router.replace('/login')
  // router.refresh()  — re-fetch server data without full page reload
  // router.back()
  // router.prefetch('/about')
}

usePathname() (Client Component only)

Returns current pathname as a string.

useSearchParams() (Client Component only)

Returns a read-only URLSearchParams object. Wrap in <Suspense> to avoid de-opting the entire page to client-side rendering.

Request Functions (Server only)

cookies()

Read and set cookies in Server Components, Server Actions, and Route Handlers.

import { cookies } from 'next/headers'

export default async function Page() {
  const cookieStore = await cookies()
  const theme = cookieStore.get('theme')?.value
}

headers()

Read request headers (read-only in Server Components).

import { headers } from 'next/headers'

export default async function Page() {
  const headersList = await headers()
  const userAgent = headersList.get('user-agent')
}

Metadata API

Static Metadata

import type { Metadata } from 'next'

export const metadata: Metadata = {
  title: 'Page Title',
  description: 'Page description',
  openGraph: { title: 'OG Title', images: ['/og.png'] },
  robots: { index: true, follow: true },
}

generateMetadata()

import type { Metadata } from 'next'

export async function generateMetadata({
  params,
}: {
  params: Promise<{ id: string }>
}): Promise<Metadata> {
  const { id } = await params
  const post = await getPost(id)
  return { title: post.title, description: post.excerpt }
}

generateStaticParams()

export async function generateStaticParams() {
  const posts = await getPosts()
  return posts.map((post) => ({ id: post.id.toString() }))
}

Cache & Revalidation

Server Lifecycle & Auth Interrupts

• after(callback) from next/server (stable since 15.1) — run work after the response (or prerender) finishes. Usable in Server Components, Server Actions, Route Handlers, and Proxy. In Server Components, read cookies()/headers() before calling after() and close over the values — they cannot be read inside the callback.
• connection() from next/server — await connection() to mark rendering as dynamic before non-API dynamic work (e.g. Math.random(), Date.now()).
• forbidden() / unauthorized() from next/navigation with forbidden.tsx/unauthorized.tsx — render 403/401 pages. Experimental — require experimental: { authInterrupts: true } (still not stable in 16.3).

Root Params (16.3)

import { lang } from 'next/root-params' — awaitable accessors for root dynamic segments (e.g. app/[lang]/), typed per segment, usable from any Server Component. Replaces unstable_rootParams (removed in 16.0).

For Image, Font, Script, next.config.ts, proxy API, cache functions with code examples, and advanced configuration, see references/advanced-api.md.